Microplates, also known as microwell plates and microtitre plates, are a standard product and are regularly used in medical, chemical, and biological laboratories. Microplates have a plurality of sample wells typically arranged in a 2:3 rectangular matrix. For example, a common configuration for a microplate has 96 wells arranged in an 8×12 matrix.
In the laboratory, microplates are commonly supplied with various liquids, e.g. samples, reagents, and solvents. The particular liquids used will depend on the test being performed. During use, it is important to the accuracy of the laboratory procedure being performed that each liquid be dispensed into the desired well without cross contamination or unintended dispensing of a liquid into the wrong well. It is also important to the efficient operation of a laboratory to be able to dispense liquids into the desired sample wells accurately and rapidly. Therefore, automated machines have been introduced for automatically dispensing desired liquids into designated wells of a microplate. Whether a liquid is dispensed into a sample well or drawn from a well, and whether dispensed manually or using an automated apparatus, the liquid is typically moved with some type of pipette.
Some laboratory procedures utilize two types of microplates, namely, filter plates and collection plates. As these terms are used herein, filter plates have wells, sometimes referred to as columns, with openings at both the top and bottom, whereas collection plates have openings at the top but are closed at the bottom. As used herein, the term “well” is used to indicate a well of a microplate having either an open bottom (sometimes referred to as a column) or a closed bottom as in a collection plate. During common procedures, an adsorbent packing material is provided in each well of a filter plate. After the sample fluid has been placed into the well, the adsorbent is washed with suitable solvents to remove unwanted compounds which are directed to a waste station. Then the filter plate is placed over a collection plate and the desired analyte is removed from the packing material using a suitable eluent and the eluate is collected in the collection plate.
When liquids are moved to any of the wells in a microplate other than the wells located on the outer perimeter of the microplate, it is necessary to move the pipette containing a liquid over wells other than the well to which the liquid is intended. This creates a risk of unintended contamination by a liquid entering a well for which it is not intended.